Method and apparatus for continuous or semicontinuous casting of metals



Oct. 26, 1954 R. CHADWICK EI'AL 2,692,410

METHOD AND APPARATUS FOR commuous 0R SEMICONTINUOUS CASTING OF METALS Filed April 9. 1954 2 Sheets-Sheet l (Z- 3 i 4 l i i W LA. Fl6.|.

I N VE TOR FIG. 2. RICHARD GIIADWIGK JOHN FRANCIS HOBBS ORNEYS R. CHADWICK METHOD AND APP ATUS F0 OR SEMICONTINUOUS CASTI ET AL 2,692,410 R cou'rmuous NG 0F METALS Oct. 26, 1954 2 Sheets-Sheet 2 Filed April 9. l95f1 FIC13.

A T TORNEYS Patented Oct. 26, 1954 UNITED STS PATENT OFFIE METHOD AND APPARATUS FOR CONTINU- OUS OR SEMICONTINUOUS CASTING F METALS mingham,

Great Britain England,

Application April 9, 1954, Serial No. 422,172

Claims priority, application Great Britain November 24, 1949 8 Claims.

This invention relates to the continuous or semi-continuous casting of metals and alloys and more particularly to improvements in the method of cooling the cast ingot. The application is a continuation-in-p-art of our copending application Serial No. 196,541, filed November 20, 1950, now abandoned.

In one method of continuous casting (the term continuous casting as used hereinafter includes both strictly continuous and semi-continuous processes) molten metal is poured into a short open mould and the emerging cast product is subjected to direct cooling by means of a water spray. This has many advantages such for example as the production of fine grain and reduction of segregation, but the disadvantage that internal stresses are set up due to the arge temperature drop from the interior to the exterior of the cast product, which are often sufficiently great to cause central cracking in cylindrical billets of certain alloys.

The object of this invention is to provide a simple and eifective method of cooling by which this tendency to cracking is substantially obviated.

According to the present invention we provide a method of direct cooling of continuously cast billets of substantially circular cross-section in which the direct chill is interrupted at one or more points around the periphery of the billet in order to prevent the coolant from making direct contact with the billet surface at the said points.

When casting in a plain mould, i. e. a singlewalled mould, this interrupted cooling is preferably effected by the provision of a deflector p ate attached to the bottom of the mould to divert the coolant at the required position or positions. When on the other hand casting is carried out in a water-jacketed mould and the direct cooling effected by means of a separate spray ring below the mould, the interruption of the cooling may be attained by the use of an incomplete ring of jets. Alternatively, when the mould coolant is also utilised for the direct chill by allowing it to flow out through an inclined annular slit or series of apertures in the base of the jacket, the direct cooling may be interrupted at the required position or positions by suitable 2 blocking of the slit or the appropriate apertures.

As the billet moves downward there are thus formed areas of billet surface which are not, at least during the critical initial period of cooling, in direct contact with the coolant and are therefore at a higher temperature than the remainder of the periphery, thus introducing points of weakness in the billet which facilitate release of stress by allowing slight distortion of the circular cross-section.

The width of the individual portions of the billet to be protected from contact with coolant varies approximately in proportion to the billet diameter. Thus for 6" diameter billets it may be 1 "-2, for 11"billets 3"-4, and for 18" billets 4: /g"-6". The proportional factor and the actual number of protected areas depend mainly upon the composition of the alloy to be cast. Some alloys are more liable to central cracking than others and require a greater width of uncooled billet; in some cases two opposed deflector plates are suflicient, whilst in others the use of four is advisable. For a given alloy composition the width of bi let to be protected is selected for optimum conditions, taking into account factors such as the rate of heat extraction employed. Thus by increasing the width beyond the minimum affording protection from central cracking, faster casting speeds can be utilised but they are liable to be accompanied by exudation of the still molten billet core through the skin, so that it is necessary to effect a compromise between rate of casting and the casting conditions under which the process is being operated.

By utilising the method according to the present invention sound castings can be produced at casting speeds at least 0.25"1" per minute higher than those attainable under corresponding conditions without the use of the interrupted chill. The method according to the invention is particularly efiicacious in the casting of aluminium base alloys.

The invention is illustrated by the accompanying diagrammatic drawings in which:

Fig. 1 is a view of part of a continuous casting machine, and

Fig. 2 is a vertical section on the line .AA in Fig. 1;

Fig. 3 is a vertical section of part of a continuous casting machine incorporating a second embodiment of the invention, and

Fig. 4 is a horizontal section on the line 13-3 in Fig. 3;

Fig. 5 is a vertical section of part of a continuous casting machine incorporating a third embodiment of the invention, and

Fig. 5 isa horizontal section on the line CC in Fig.5.

Referring to Figs. 1 and 2 of the drawing, i represents a continuously cast billet emerging from the mould 2. A ring of water sprays 3 applies coolant to both the :lower end of the, mould and the emerging metal as indicated. A deflector plate 4 is attached to the lower end of the mould and is of widthsuch that the coolant is substantially prevented from making direct contact with the billet over the shaded area of surface indicated in Fig. 1.

Referring to Figs. 3 and 4, 5represents a continuously cast billet emerging from the mould 5 which is fitted with a water-jacket l. A sprayring 8 is located below the mould exit, and supplies coolant water for the direct cooling of the emergent billet. The orifices 9 in the spray-ring are disposed in such manner that on four equidistantly spaced .portions :of the billet there is no impingement of coolant from the spray-ring.

Referring to Figs. 5 and 6, l represents a continuously cast billet emerging from the mould H which is provided with a water-jacket l2. Water enters the jacket at the inlet 13 and after cooling the mould leaves the jacket by means of an inclined annular slit M in the base of the latter and impinges on the emergent billet, thus providing direct cooling for the billet. The slit H3 is'bl'ocked over part of its length at the diametri 'cally opposed portions 15 and I6, thus preventing 11 fD fl c Limgtmg Deta so e co or cas ing Bfllet plates speed,

ins/min.

not usually necessary 2 plates, each 3 wide. 3 'Zplates, each wide 2. 5

By way of comparison the limiting casting speed for an 11" billet of the same alloy under corresponding conditions without the deflector plates was only 1.75" per minute.

Example 2 Limiting casting speeds at which no central cracking occurred were determined in similar manner for the same range of billet diameters in an aluminium base alloy containing 0.7% magnesium, 1.1% silicon, 0.6% manganese, 0.25% iron, balance aluminium, which is a more difficult alloy to cast than that of Example 1, using deflector plates attached to the mould in 4 the manner shown in Figs. 1 and 2 of the drawings.

- Limiting gi p Details of Deflector plates 33123? ins/min.

2 plates, each 3 wide 3 2 plates, each 3" wide and 2 4 plates 2 2 4'. plates and 25 plates. 1. 5

By way of comparison, an 11" billet of the same alloy cast under corresponding conditions without the deflector plates still cracked at a casting speed (if-1 .75" per minute.

Where in these examples two deflector plates were employed they were positioned at diametrically opposed positions, and where four were used they were equispaced around the mould periphery, plates of the same size being opposite each other.

We claim:

1. In a method for the manufacture of billets of large diameter and of substantially circular cross-section by a continuous or semi-continuous casting process in which the billet is directly contacted with a coolant as it emerges from the mold in which it was-cast, the improvement which comprises reducing the tendency of said billet to crack centrally by preventing said coolant from directly contacting said billet at at least one region around the circumference of the billet while the billet is advancing in order to prevent the coolant from making contact with a lengthwise section of the billet to thus prevent contact of said coolant with a substantial minor portion of the billet at the said regions, while directly contacting the remaining portions of said billet with said coolant.

2. The improvement recited inclaim 1 in which said substantial minor portion does not exceed ]about 40% of the circumferential length of said illet.

3. The improvement recited in claim :1 in which said regions have -a 'width'of'at least 8% of the circumferential length of said billet.

4. Apparatus for the continuous or semi-"continuous casting of billets of large diameter and substantially circular cross-section which comprises a mold having a cylindrical inner molding surface, coolant supply means disposed around the periphery of the billet at itsxpoint of egress from the mold for directing liquid coolant directly against the periphery off't'he billet where the billet emerges from the mold and means to prevent direct contact of the coolant with predetermined substantial minor peripheral regions while permitting said coolant to directly contact the remainder of the periphery of said billet to thereby introduce points of weakness in the billet which facilitate release of stress :by permitting slight distortion of the cross-sectional configuration;

5. Apparatus as recited in claim 4 in which contact of the coolant with the billet is prevented by means of a deflector plate interposed between the coolant supply means and the 'periphery of the billet.

6. Apparatus as recited in claim 5 in which said deflector plate is secu'red to the bottom of determined substantial minor peripheral regions o f said billet is prevente'dwhile the-coolantds permitted to directly contact the remainder of the periphery of said billet by employing an incomplete ring of coolant jets as said coolant supply means.

8. Apparatus as recited in claim 4 in which said mold is jacketed and the base of said mold jacket is fitted with a series of apertures to direct the coolant within said mold jacket directly against the periphery of the billet where the billet emerges from the mold and means to 10 1503479 block said apertures at positions to prevent direct contact of said coolant with predetermined substantial minor peripheral regions of said bil- 6 let while permitting said coolant to directly contact the remainder of the periphery of said billet.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 831,184 Pehrson Sept. 18, 1906 Coats Aug. 5, 1924 2,304,258 Junghans Dec. 8, 1942 2,414,269 Nicholls Jan. 14, 1947 2,515,284 Zeigler et a1 July 18, 1950 

